I was debating on the tunze nano ATO, but I keep seeing mixed reviews, and heard it's a pain to mount on a tank with a rim. Any suggestions, or is the tunze the way to go?Try to invest in an auto top off then. It helps in a smaller tank and your back will thank you. I have never seen my scarlets fight with any of my blue or red hermits. So for me, they are the least aggressive. I really don’t think they’re fighting for shells yet when you just recently got them.